Use client generator to generate all k8s clients and add respective client-go metrics (#2668)

* Define client generator to generate all k8s clients
* Increase QPS and burst values
* Capture client-go metrics
* Support for controller runtime metrics

Signed-off-by: Sanket Sudake <sanketsudake@gmail.com>

pkg/crd/client.go

@@ -19,7 +19,6 @@ package crd
 import (
 	"context"
 	"errors"
-	"os"
 	"time"
 
 	"go.uber.org/zap"
@@ -29,64 +28,76 @@ import (
 	"k8s.io/client-go/kubernetes"
 	_ "k8s.io/client-go/plugin/pkg/client/auth"
 	"k8s.io/client-go/rest"
-	"k8s.io/client-go/tools/clientcmd"
 	metricsclient "k8s.io/metrics/pkg/client/clientset/versioned"
+	"sigs.k8s.io/controller-runtime/pkg/client/config"
 
 	"github.com/fission/fission/pkg/generated/clientset/versioned"
 	"github.com/fission/fission/pkg/utils"
 )
 
-// GetKubernetesClient gets a kubernetes client using the kubeconfig file at the
-// environment var $KUBECONFIG, or an in-cluster config if that's
-// undefined.
-func GetKubernetesClient() (*rest.Config, kubernetes.Interface, apiextensionsclient.Interface, metricsclient.Interface, error) {
-	var config *rest.Config
-	var err error
-
-	// get the config, either from kubeconfig or using our
-	// in-cluster service account
-	kubeConfig := os.Getenv("KUBECONFIG")
-	if len(kubeConfig) != 0 {
-		config, err = clientcmd.BuildConfigFromFlags("", kubeConfig)
-		if err != nil {
-			return nil, nil, nil, nil, err
-		}
-	} else {
-		config, err = rest.InClusterConfig()
-		if err != nil {
-			return nil, nil, nil, nil, err
-		}
-	}
-
-	// creates the clientset
-	clientset, err := kubernetes.NewForConfig(config)
-	if err != nil {
-		return nil, nil, nil, nil, err
-	}
-
-	apiExtClientset, err := apiextensionsclient.NewForConfig(config)
-	if err != nil {
-		return nil, nil, nil, nil, err
-	}
-
-	metricsClient, _ := metricsclient.NewForConfig(config)
-
-	return config, clientset, apiExtClientset, metricsClient, nil
+type ClientGenerator struct {
+	restConfig *rest.Config
 }
 
-func MakeFissionClient() (versioned.Interface, kubernetes.Interface, apiextensionsclient.Interface, metricsclient.Interface, error) {
-	config, kubeClient, apiExtClient, metricsClient, err := GetKubernetesClient()
-	if err != nil {
-		return nil, nil, nil, nil, err
+func (cg *ClientGenerator) getRestConfig() (*rest.Config, error) {
+	if cg.restConfig != nil {
+		return cg.restConfig, nil
 	}
 
-	// make a CRD REST client with the config
-	crdClient, err := versioned.NewForConfig(config)
+	var err error
+	cg.restConfig, err = config.GetConfig()
 	if err != nil {
-		return nil, nil, nil, nil, err
+		return nil, err
 	}
+	return cg.restConfig, nil
+}
 
-	return crdClient, kubeClient, apiExtClient, metricsClient, nil
+func (cg *ClientGenerator) GetFissionClient() (versioned.Interface, error) {
+	config, err := cg.getRestConfig()
+	if err != nil {
+		return nil, err
+	}
+	return versioned.NewForConfig(config)
+}
+
+func (cg *ClientGenerator) GetKubernetesClient() (kubernetes.Interface, error) {
+	config, err := cg.getRestConfig()
+	if err != nil {
+		return nil, err
+	}
+	return kubernetes.NewForConfig(config)
+}
+
+func (cg *ClientGenerator) GetApiExtensionsClient() (apiextensionsclient.Interface, error) {
+	config, err := cg.getRestConfig()
+	if err != nil {
+		return nil, err
+	}
+	return apiextensionsclient.NewForConfig(config)
+}
+
+func (cg *ClientGenerator) GetMetricsClient() (metricsclient.Interface, error) {
+	config, err := cg.getRestConfig()
+	if err != nil {
+		return nil, err
+	}
+	return metricsclient.NewForConfig(config)
+}
+
+func (cg *ClientGenerator) GetDynamicClient() (dynamic.Interface, error) {
+	config, err := cg.getRestConfig()
+	if err != nil {
+		return nil, err
+	}
+	return dynamic.NewForConfig(config)
+}
+
+func NewClientGenerator() *ClientGenerator {
+	return &ClientGenerator{}
+}
+
+func NewClientGeneratorWithRestConfig(restConfig *rest.Config) *ClientGenerator {
+	return &ClientGenerator{restConfig: restConfig}
 }
 
 // WaitForCRDs does a timeout to check if CRDs have been installed
@@ -111,29 +122,3 @@ func WaitForCRDs(ctx context.Context, logger *zap.Logger, fissionClient versione
 		}
 	}
 }
-
-// GetDynamicClient creates and returns new dynamic client or returns an error
-func GetDynamicClient() (dynamic.Interface, error) {
-	var config *rest.Config
-	var err error
-
-	// get the config, either from kubeconfig or using our
-	// in-cluster service account
-	kubeConfig := os.Getenv("KUBECONFIG")
-	if len(kubeConfig) != 0 {
-		config, err = clientcmd.BuildConfigFromFlags("", kubeConfig)
-		if err != nil {
-			return nil, err
-		}
-	} else {
-		config, err = rest.InClusterConfig()
-		if err != nil {
-			return nil, err
-		}
-	}
-	dynamicClient, err := dynamic.NewForConfig(config)
-	if err != nil {
-		return nil, err
-	}
-	return dynamicClient, nil
-}